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THREE-SLOT INVERSE GENEVA WHEEL MECHANISM

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Driver 1 rotates about fixed axis A and carries pin a which consecutively engages straight radial slots d of Geneva wheel 2. Geneva wheel 2 rotates about fixed axis B and its slots d are located symmetrically at angles of 120° between the axes of adjacent slots. Driver 1 has concentric locking surface b which engages concave locking surfaces e of Geneva wheel 2 durinig its idle periods. When driver 1 rotates continuously at uniform velocity, driven Geneva wheel 2 rotates intermittently at nonuniform velocity and has three rotation periods tᵣ and three idle periods tᵢ. Locking surfaces b and e prevent unintentional rotation of Geneva wheel 2 during its idle periods. The time of one revolution of driver 1 is T=tᵣ+tᵢ. The angles of rotation of driver 1 corresponding to an idle and to a rotation period of Geneva wheel 2 equal ϕᵢ=60° and ϕᵣ=300°. The angle of rotation of Geneva wheel 2 to each revolution of driver 1 is ϕ_G= 120°. The rotation and idle factors are p=tᵣ/T=0.8333 and q=tᵢ/T=0.1667. The working time coefficient is k=p/q=5. The transmission ratio from the Geneva wheel to the driver is i₂₁=ω₂/ω₁=(λ(cos(ϕ₁)-λ))/(1-2λ cos(ϕ₁)+λ²) where λ=R/L, R is radius A͞D, L is centre-to-centre distance A͞B, ϕ₁ is the instantaneous angle of rotation of driver 1 measured from line AB, and ω₁ and ω₂ are the angular velocities of driver 1 and Geneva wheel 2. The maximum value of the transmission ratio is i₂₁=ω₂/ω₁=0.464. Coefficient χ characterizes the angular acceleration ε₂ of Geneva wheel 2 at the instants when pin a begins and ends engagement with slot d, and equals χ=ε₂/ω₁²=1.729. Driver 1 and Geneva wheel 2 rotate in the same direction.
$2626$FG,GW$

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